The present disclosure generally relates to catalytic plate reactors. In various examples, methods for designing and operating catalytic plate reactors employed in steam methane reforming are described.
The rapid development of distributed methane sources (e.g., shale gas formations and landfill capture, gas associated with oil or coal deposits) has augmented the technological push for localized processing of methane for the production of easily transportable or high value chemicals and fuels, such as Fischer-Tropsch products and hydrogen. See, for example, A. Burnham, J. Han, C. Clark, M. Wang, J. Dunn, and I. Palou-Rivera, “Life-Cycle Greenhouse Gas Emissions of Shale Gas, Natural Gas, Coal, and Petroleum,” Env. Sci. & Tech., vol. 46, no. 2, pp. 619-627, 2012; S. Kemball-Cook, A. Bar-Ilan, J. Grant, L. Parker, J. Jung, W. Santamaria, J. Mathews, and G. Yarwood, “Ozone Impacts of Natural Gas Development in the Haynesville Shale,” Env. Sci. & Tech., vol. 44, no. 24, pp. 9357-9363, 2010; D. Kargbo, R. Wilhelm, and D. Campbell, “Natural Gas Plays in the Marcellus Shale: Challenges and Potential Opportunities,” Env. Sci. & Tech., vol. 44, no. 15, pp. 5679-5684, 2010; R. Howarth, R. Santoro, and A. Ingraffea, “Methane and the greenhouse-gas footprint of natural gas from shale formations,” Climate Change, vol. 106, no. 4, pp. 679-690, 2011; S. Osborn, A. Vengosh, N. Warner, and R. Jackson, “Methane contamination of drinking water accompanying gas-well drilling and hydraulic fracturing,” Proceedings of the National Academy of Sciences of the United States of America, vol. 108, no. 20, pp. 8172-8176, 2011; N. Muradov, F. Smith, and A. T. Raissi, “Hydrogen production by catalytic processing of renewable methane-rich gases,” Int. J. of Hydrogen Energy, vol. 33, no. 8, pp. 2023-2035, 2008. Localized production facilities should be efficient, robust and scalable at low throughput.
Catalytic plate microreactors (CPRs) have proven to be one of the most successful and promising solutions in this area. See, for example, S. Becht, R. Franke, A. Geisselmann, and H. Hahn, “An industrial view of process intensification,” Chem. Eng. and Proc., vol. 48, no. 1, pp. 329-332, 2009; M. Mettler, G. Stefanidis, and D. Vlachos, “Scale-out of Microreactor Stacks for Portable and Distributed Processing: Coupling of Exothermic and Endothermic Processes for Syngas Production,” Ind. Eng. Chem. Res., vol. 49, no. 21, pp. 10 942-10 955, 2010; S. Karagiannidis and J. Mantzaras, “Numerical investigation on the start-up of methane-fueled catalytic microreactors,” Combustion and Flame, vol. 157, no. 7, pp. 1400-1413, 2010; M. Mettler, G. Stefanidis, and D. Vlachos, “Enhancing stability in parallel plate microreactor stacks for syngas production,” Chem. Eng. Sci., vol. 66, no. 6, pp. 1051-1059, 2011. CPRs consist of alternating millimeter-sized channels, separated by catalyst-coated plates. In the case of steam-methane reforming, the endothermic reforming reactions are supported by the exothermic catalytic combustion of methane, occurring in parallel, alternate channels. CPRs can achieve higher conversions than conventional reactors with an order-of-magnitude reduction in catalyst volume. See, for example, G. Kolios, J. Frauhammer, and G. Eigenberger, “Efficient reactor concepts for coupling of endothermic and exothermic reactions,” Chem. Eng. Sci., vol. 57, no. 9, pp. 1505-1510, 2002, 2nd International Symposium on Multifunctional Reactors (ISMR-2), Nurnberg, Germany, Jun. 25-28, 2001; M. Zanfir and A. Gavriilidis, “Catalytic combustion assisted methane steam reforming in a catalytic plate reactor,” Chem. Eng. Sci., vol. 58, no. 17, pp. 3947-3960, 2003; M. Baldea and P. Daoutidis, “Dynamics and control of autothermal reactors for the production of hydrogen,” Chem. Eng. Sci., vol. 62, pp. 3218-3230, 2007; M. Zanfir, M. Baldea, and P. Daoutidis, “Optimizing the Catalyst Distribution for Countercurrent Methane Steam Reforming in Plate Reactors,” AIChE J., vol. 57, no. 9, pp. 2518-2528, 2011. However, the aforementioned studies have also indicated several potential operational issues, such as flow maldistribution and local temperature rises (“hotspots”) with deleterious effects on the integrity of the catalyst coatings and supporting plates. Several design modifications have been proposed to mitigate these issues, including using a distributed catalyst activity, distributed fuel feeds, reverse flow configurations or offsetting the catalyst coating in the reforming and combustion channels. See, for example, M. Zanfir and A. Gavriilidis, “Influence of flow arrangement in catalytic plate reactors for methane steam reforming,” Chem. Eng. Res. & Des., vol. 82, no. A2, pp. 252-258, February 2004, 3rd International Symposium on Multifunctional Reactors (ISMR3)/18th Colloquia on Chemical Reaction Engineering (CCRE18), Bath, England, 2003; G. Kolios, B. Glockler, A. Gritsch, A. Morino, and G. Eigenberger, “Heat-integrated reactor concepts for hydrogen production by methane steam reforming,” Fuel Cells, vol. 5, no. 1, pp. 52-65, 2005; M. van Sint Annaland and R. Nijssen, “A novel reverse flow reactor coupling endothermic and exothermic reactions: an experimental study,” Chem. Eng. Sci., vol. 57, no. 22-23, pp. 4967-4985, 2002; R. Ramaswamy, P. Ramachandran, and M. Dudukovic, “Recuperative coupling of exothermic and endothermic reactions,” Chem. Eng. Sci., vol. 61, no. 2, pp. 459-472, 2006; M. Zanfir, M. Baldea, and P. Daoutidis, “Optimizing the Catalyst Distribution for Countercurrent Methane Steam Reforming in Plate Reactors,” AIChE J., vol. 57, no. 9, pp. 2518-2528, 2011.
Furthermore, CPRs operation is subject to fluctuations in the quality of the feedstock, including changes in pressure, purity and composition with potentially serious operational consequences. For example, a rapid change in methane composition can cause significant temperature increases in the reactor. In addition, practical considerations pertaining to the design and dimensions of CPRs may limit the availability of distributed measurements (e.g., the constructive challenges and cost of locating temperature sensors in a multi-plate stack) and actuators (e.g., it may not be economically feasible to control the flow to each channel).